Totally, I have found 34 appearances in the ext-theme-classic CSS file. I guess to fix the issue it needs to override them all. Moveover, for each theme (not sure about Neptune). Well, it is going to be complicated to override everything.

Another aspect.

This "-frameInfo" postfix thing is managed within the Ext.util.Renderable class which is mixed into the Ext.AbstractComponent class. I have extracted the related changes.